Device for postoperative fixation back into the cranium of a plug of bone removed therefrom during a surgical operation

ABSTRACT

A device for rapid reattachment of a bone flap to a cranium after a surgical operation is provided. The device comprises a pin comprising an elongated shaft, an inner disk and an outer disk. At least the outer disk comprises a central bore. The pin and inner disk are adapted to be assembled together to form a pin and inner disk assembly such that the inner disk is located at one end of the pin. The outer disk is adapted to be mounted on the shaft of the pin with the shaft of the pin extending through the central bore of the outer disk. The device is operated by (i) positioning the inner disk on the inside of the cranium with the shaft of the pin extending through the kerf between the bone flap and the cranium, (ii) forcing the outer disk downwardly on the shaft of the pin toward the inner disk until the outer disk securely engages the outside of the bone flap and the cranium, such that the bone flap is securely held in place between the inner disk and the outer disk, and (iii) trimming off an excess portion of the shaft extending out beyond the outer disk.

This application is a continuation of prior U.S. Pat. Application Ser.No. 09/494,599, filed Jan. 31, 2000, now U.S. Pat. No. 6,270,500, whichis a continuation of U.S. Pat. Application Ser. No. 09/088,175, filedJun. 1, 1998, now U.S. Pat. No. 6,068,631, which is a continuation ofU.S. Pat. Application Ser. No. 08/790,071, filed Jan. 28, 1997, now U.S.Pat. No. 5,800,436.

BACKGROUND OF THE INVENTION

The present background of the invention concerns a device forpostoperative fixation back into the cranium of a plug of bone removedtherefrom during a surgical operation.

It is often necessary during brain surgery to remove a plug of bone fromthe cranium to provide the surgeon with access to the field ofoperation. The plug is sawed out and must be replaced in the craniumafter the operation and fixed thereto. Such plugs have long been fixedback into the rest of the cranium by suturing with loops of steel wirethat extend through both and then twisting together the projecting endsof the emplaced loops. The contact between the plug and the rest of thecranium is relatively unstable, however. The two halves do not fusetogether very well. The scalp can also become inflamed. Another drawbackto such an approach is that the wire considerably distorts the imagesobtained in postoperative computerized tomography and accordinglyimpedes definitive interpretation of the soft structures of the brain.Although using nonresorbable and physiologically compatible threadinstead of wire does eliminate the last-mentioned drawback, the fixationof the plug to the rest of the skull is still unstable. The two partscan also be fixed with thin plates of compatible metal, titanium forinstance (EP A 0 510 390). Such plates bridge the abutment between theparts and are screwed to both, also closing off bores introduced intothe cranium prior to section. This approach, however, is also not verysatisfactory. It is both complicated and time-consuming and hence notinexpensive.

SUMMARY OF THE INVENTION

With the aforesaid state of the art as a point of departure, the objectof the present invention is a simpler and more rapid device for accurateand permanent postoperative fixation back into the cranium of a plug ofbone removed therefrom during a surgical operation.

This object is attained in accordance with the present invention in adevice of the aforesaid genus comprising a pin and two concavoconvexdisks of a physiologically compatible metal or metal compound. The pinhas a flat head at one end and one of the disks comes to rest againstthe head. Each disk has row of teeth extending along the edge of theconcave side and a bore through the center. The shaft of the pin fitsinto the bore. The disks can be mounted on the shaft with the teeth oneach one facing the teeth on the other. The second disk can be fastenedto the shaft.

The inner disks in the aforesaid fixation device in accordance with thepresent invention are secured to the pins in the vicinity of the head.The disks are then inserted through a slightly larger recess in thecircumference of the plug, below the parts of the joint, with the shaftof the pin projecting out of the kerf between the plug and the rest ofthe cranium. The outer disk is then mounted over the section of pinprojecting out of the kerf. The two disks are then approached untiltheir teeth bite into the edges of both the plug and of the rest of thecranium. The second disk is then secured to the shaft.

Titanium is particularly appropriate for the physiologically compatiblemetal. Such titanium alloys as Ti₆A₆ Va are also appropriate. A devicemade of titanium is of advantage because it will not distortpostoperative computerized-tomography images. The inner disk can bemounted more stable on the shaft of the pin if the transition betweenthe head of the pin and the shaft is conical and dimensioned to ensurethat a disk resting against the head will be forced tight around theshaft. Slits can also extend radially outward from the bore through thefirst disk to be mounted on the shaft. The center of the disk can bedepressed. Areas can be removed from the disks at regular intervalsbetween the bore and the edge to conserve material. The device can beapplied to the two halves of bone by a procedure similar in principle toblind riveting. Notches can accordingly be introduced into each shaft toprevent the second disk mounted thereon from sliding away from the headof the pin. If the second disk on the shaft is deformed in a directionopposite that of its concavoconvexity, the deformation alone will secureit to the shaft by compression. The shaft can also be threaded andaccommodate a nut. The nut can be tightened against the second disk. Thesecond disk will in every case be displaced until its teeth engage thetwo halves of the joint, creating the desired fixation of the plug backinto the rest of the cranium at the adjacent edges.

The novel device can be easily and rapidly manipulated and accomplishesthe desired accurate and permanent postoperative fixation back into thecranium of a plug of bone removed therefrom during a surgical operation.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be specified with reference to theaccompanying drawing wherein

FIG. 1 is an exploded view of the device in accordance with the presentinvention,

FIG. 2 is a view in the direction indicated by arrow II in FIG. 1 of oneembodiment of the first disk mounted over the shaft of the pin,

FIG. 3 is a view in the direction indicated by arrow III in FIG. 1 ofone embodiment of the second disk mounted over the shaft of the pin,

FIG. 4 is a longitudinal section of the components of the deviceassembled,

FIG. 5 illustrates how the device in accordance with the presentinvention can be employed,

FIG. 6 is a section along the line VI—VI in FIG. 5,

FIG. 7 is a schematic view and shows another embodiment of the presentinvention, and

FIG. 8 is a schematic view of a still further embodiment according tothe present invention; and

FIG. 9 is a longitudinal section of another embodiment of a device inaccordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A device for postoperatively fixing back into the cranium a plug of boneremoved therefrom during a surgical operation comprises a pin 11 and twoconcavoconvex disks 21 and 22. The pin comprises a shaft 112 and a head111, Disk 21, the inner disk, is mounted on the shaft first and comes torest against the inner surface of the plug and of the rest of thecranium that are to be united. Disk 22, the outer disk, is mounted onthe shaft next and comes to rest against the outer surface of the plugand the rest of the cranium. There is a hole 211 through the center ofeach disk 21 and a hole 221 through the center of each disk 22. Theshaft 112 of pin 11 extends through the holes 211 and 221 of the disksin the assembled device. A raw of teeth 213 extends along the edge 212of the concave side of disk 21, and a row of teeth 223 extends along theedge 222 of the concave side of disk 22. As will be evident from FIGS. 1and 4, disks 21 and 22 are mounted on the shaft 112 of pin 11 with theirteeth facing each other.

Shaft 112 fits tightly in the hole 211 through disk 21. Any disk can beprovided as illustrated in FIG. 2 with slits 214 extending radiallyoutward from the hole 211 through its center. If the transition betweenthe head 111 and the shaft 112 of pin 11 is conical, slits 214 will asis desirable accurately position the disk in relation to the pin, bothof which will accordingly support both the plug and the rest of thecranium once the device has been emplaced, The area between the holethrough the center of any disk and its circumference can also beprovided as illustrated in FIG. 3 with perforations 226 to conservematerial and decrease weight. Each disk can have both slits 214 andperforations 226.

FIGS. 5 and 6 illustrate how the device is employed. FIG. 5 illustratespart of an adult cranium 31 from which a plug 32 of bone has been sawnto provide access to the brain, which is available to the surgeonthrough aperture 33. A recess 321 slightly larger than the disks hasbeen removed from plug 32 at its circumference. once the operation isover, the plug is returned to the aperture 33. Inner disks 22 aremounted on the shafts 112 of pins 11. The inner disks are inserted oneby one through recess 321 with the shafts projecting out and slid alongthe inner surface of the plug and residual cranium with the shaftsextending out of kerf 331 in the directions indicated by arrows A inFIG. 5 until they arrive at the point where they are to be positioned.outer disks 22 are now mounted on the shafts of the pins in situ. Theouter disks are finally secured to the shafts with a tool of the typeemployed to fasten blind rivets. The tool forces outer disks 22 andinner disks 21 together in the direction indicated by arrow B in FIG. 6until the teeth on each disk bite into the tissue of the plug and of theresidual cranium, securing the two together. The section of each shaftextending out beyond the outer disk is now trimmed off. The shaft canalternatively be threaded, and the disks forced together over thethreads until the teeth bite into the tissue.

Thus, in another embodiment shown in FIG. 7, as well as in FIG. 9, theshaft 112 of the pin 11 has nothces 112 c engaging the outer surface ofthe second disc 22 and forcing it towards the head 111 of the pin.

In the embodiment of FIG. 8, the shaft of the pin 11 has a thread 112 aand accommodates a nut 112 b that can be screwed against the second disk22.

In the embodiment shown in FIG. 9, the first disk 21 a and the seconddisk 22 a are each formed in a generally concavoconvex shape with acenter portion 218, 228 of the disk being depressed in a directionopposite that of its concavoconvexity.

What is claimed is:
 1. A method for constructing and using a device forrapid reattachment of a bone flap to a cranium after a surgicaloperation, wherein the method comprises: (i) constructing a devicecomprising: (a) a pin comprising and elongated shaft; (b) an inner disk;and (c) an outer disk, wherein the outer disk comprises a central bore;(ii) assembling the pin and inner disk together to form a pin and innerdisk assembly such that the inner disk is located at one end of the pin;(iii) mounting the outer disk on the shaft of the pin with the shaft ofthe pin extending into and out of the central bore of the outer disk;(iv) positioning the device such that the inner disk is positioned inthe inside of the cranium with the shaft of the pin extending into andout of the kerf between the bone flap and the cranium; (v)longitudinally moving the outer disk downwardly on the shaft of the pintoward the inner disk until disk securely engages the outside of thebone flap and the cranium, such that the bone flap is securely held inplace between the inner disk and the outer disk; and (vi) trimming offan excess portion of the shaft extending out beyond the outer disk.